EP0372348B1 - Packaging for sliced food, particularly for sliced cheese - Google Patents

Description

The invention relates to a packaging suitable for disk-shaped foods, such as cheese slices, with a substantially rectangular surface, made of a film which is wrapped around the food to be packaged as a flat tube and completely encloses it, the two longitudinal axial edge zones of the film overlapping, are connected to one another by a strip-shaped heat seal layer in the vicinity and parallel to an edge of the film and the heat seal layer consists essentially of heat sealable olefin copolymer.

Patent Abstracts of Japan, vol. 9339, dated December 25, 1985, describes a device with which a strip of a heat-sealable resin is continuously bonded to a film material. For this purpose, a heat seal layer is applied in strips in the vicinity and parallel to an edge of the film material, the heat seal layer essentially consisting of heat-sealable olefin copolymer, and then the other edge of the film material is placed on the strip-shaped heat seal layer and connected to it under pressure and heat. In this way, the film material is formed into a cylinder, which is cut to a predetermined length.

To produce a packaging of the type described in the opening paragraph, it is known to form the film Form the tube and pour the heated, viscous cheese mass into the tube. The filled tube is flattened and the ribbon-shaped strand of cheese is divided by transverse web-like zones into individual, still connected, filled sections. To cool and solidify the hot cheese mass, the ribbon-shaped film-cheese tube is passed through a water bath and the outside of the film is then blown with air to remove the water that is still adhering. The tube is then divided into individually packaged cheese slices in the area of the transverse web-like zones and the individual packs are stacked.

Up to now, polyester films have been used for the production of packaging of this type, which were initially provided with a heat-sealable coating over the entire surface, and then printed on their coated surface in a further step. This process has the disadvantage that it requires a number of process steps and is therefore very complex.

In the films used to date, a relatively large amount of residual moisture remains adhering to the film surface after being blown with air. This residual moisture worsens the coefficient of friction of the film surface and causes problems when stacking the individual packages, which results in high reject rates during sorting and stacking.

The object of the invention is to improve the known packaging so that the residual moisture still adhering to the coefficient of friction of the packaging surface, even if it is printed, does not deteriorate, but practically withstands the comparison to the dry condition of the packaging surface.

This object is achieved in such a way that the outside of the packaging has a coating of an organosilicon compound, in particular of polydialkylsiloxane, and that the film is optionally printed outside of the heat seal layer.

The film suitable for producing the packaging consists of a single-ply or a coextruded multilayer polyester film, in particular a polyethylene terephthalate film, which is oriented by biaxial stretching and fixing. Their density is usually less than 1.4 g / cm³, their thickness is in the range from 8 to 30, in particular 10 to 23, micrometers. Films can likewise consist of transparent or opaque, single-ply or of a coextruded multilayer, biaxially stretched polyolefin film, the base layer essentially consisting of propylene polymers and the cover layers on one or both sides of olefin polymers, in particular propylene polymers. Their density is between 0.55 and 0.91 g / cm³, their thickness in the range of 8 to 50, in particular 10 to 40 micrometers.

With the invention, the advantages are achieved that the packaging is easier to manufacture, the sealing temperature is relatively low, so that even a short exposure time of the sealing tools creates sufficient adhesion and sealed packaging is tightly closed, but can still be easily opened by hand.

The heat-sealable olefin copolymer preferably comprises ethylene and optionally propylene and / or butylene units and is applied to the film in aqueous dispersion, the solids content of the dispersion usually being 40 to 70% by weight, based on the total weight of the dispersion. After the dispersion medium has been removed, a strip-like coating is obtained from the olefin copolymer. The thickness of the Layer depends on the desired seal seam strength. A layer thickness of 1 to 5 micrometers is usually applied. The strip-shaped, heat-sealable layer extends in the vicinity and parallel to an edge zone of the film web and usually has a width of 1 to 10 mm, in particular 2 to 4 mm.

In a preferred embodiment, the packaging has on its outside a water-repellent layer based on organosilicon compounds, preferably polydialkylsiloxane, the alkyl radicals in particular having 1 to 4 carbon atoms. The polydialkylsiloxane is particularly preferably a polydimethylsiloxane. The polydialkylsiloxane, in particular polydimethylsiloxane, has a kinematic viscosity of 10³ to 10⁵, in particular 5,000 to 50,000 mm² / s (25 ° C). The application weight of the component is preferably between 0.01 and 20 g / m², in particular 0.05 to 1 g / m².

DE-OS 35 09 384 has already disclosed a polyolefin film in which one sealable surface layer contains polydialkylsiloxane incorporated and the other sealable surface layer has polydialkylsiloxane only on the outer surface, and the multilayer film of DE-OS 35 17 795 also contains at least in one of the two non-sealable surface layers is a polydialkylsiloxane. Both films are also to be used for packaging purposes. However, neither publication can give the person skilled in the art an indication of the solution to the present problem, namely to prevent the insufficiently dried packaging from blocking.

The application of the strip-like layer of heat-sealable olefin copolymer, the printing and, if appropriate, the full application of the additive component for water-repellent impregnation and for improving the coefficient of friction in the form of polydialkylsiloxane take place simultaneously in one operation, so that one or two further operations are saved. In the process for producing the film, the silicon-organic compound is expediently first applied to the film and immediately afterwards the film is provided with the sealable strip and printed. The application of the heat-sealable polymer and the organosilicon compound and the printing on the film surface are expediently carried out on the same gravure or flexographic printing system.

To produce the packaging, the goods to be packed, e.g. B. a rectangular cheese slice, wrapped tightly by the web-shaped tubular flat film and the two overlapping edge zones of the flat film sealed in the heat in the area of the heat-sealable layer. For this purpose, a tube is usually first formed from the flat film on a vertical form-fill and seal machine and the longitudinal-axial seam is formed along the strip-shaped sealing layer. At the same time, the food is filled into the tube in a pasty form from above. The filled tube is flattened and compressed in transverse web-like zones until the pasty food between the two layers of film is almost completely removed is. After passing through a cold water bath, the flat film tube is cut at right angles to the sealed seam in the web-like zones. In the two separating edges, the packaging is closed only by pressing the film layers lying one above the other, the film layers, however, being bonded to one another by small amounts of intermediate food which has solidified as a result of the cooling.

The following example illustrates the improved surface properties and the heat sealability of the films to be used for packaging.

A single-layer, biaxially stretch-oriented polyethylene terephthalate film (PETP) with a thickness of 12 micrometers and a coextruded three-layer, non-sealable polypropylene film (BOPP) with a thickness of 15 micrometers are flexo-printed with polydimethylsiloxane, kinematic viscosity 30,000 mm² / s (25 ° C) , fully coated; immediately thereafter, an aqueous dispersion of ethylene-propylene copolymer is applied in strip form in flexographic printing and the film surface is provided with a colored printed image by flexographic printing. The application of the two connections and the printing take place in the same printing press.

For comparison, another pattern made of PETP film is printed analogously and with a full-surface coating of heat-sealable vinylidene chloride copolymer (PVDC), application in aqueous dispersion. Coating with polydimethylsiloxane is not necessary.

The measurement of the coefficient of friction takes place according to TNO (published in "Measurement of coefficient of friction at flexible packaging materials", JW Dorsteen and E. Mot, Packaging India, Vol. 5, No. 3, April / June 1973) before and after water contact Contact with water and blowing off water with air. Coefficient of friction before contact with water after contact with water and drying PETP / sealing strips 0.10 - 0.15 0.12 - 0.17 BOPP / sealing strips 0.10 - 0.15 0.12 - 0.17 PETP / PVDC 0.20-0.25 0.25-0.30

After being blown with air, the PETP and BOPP films had less water adhesion to the film surface than the PVDC-coated PETP film.

To check the seal seam strength, test strips 10 cm long and 15 mm wide are cut from the three samples and sealed against a test strip made of uncoated polyester and polypropylene film at 120 ° C and 5 bar pressure for 0.5 s. When the PVDC coating is sealed against an uncoated polyester film, there is no connection; on the other hand, the force required is around that Peel off the polyester film and polypropylene film with the ethylene copolymer layer from the uncoated film sealed against it, 0.5 to 0.8 N / 15 mm.

The single figure shows an embodiment of the packaging in perspective. A rectangular cheese slice 9 is completely enveloped by the tight-fitting flat film 1. The overlapping edge zones 2, 3 of the film 1, which is bent in a tube shape around the cheese slice, are connected to one another in the area of the strip-shaped heat seal layer 4 made of ethylene copolymer, the heat seal layer 4 extends in the vicinity and parallel to the edge 12 of the film 1. With 5, a printed field is shown schematically shown and with 13 the full surface coating with polydialkylsiloxane. The printing ink is on the layer of polydialkylsiloxane. At right angles to the heat-sealing layer 4, web-like regions 6, 7 extend in the right and left of the packaged cheese slice, in which the two layers of film 10, 11 lying one above the other only adhere to one another through an extremely thin cheese layer 8 enclosed between them. In the area of the packaging, which extends between the two areas 6 and 7, the cheese layer is much thicker, usually a few millimeters.

Claims (2)

1. Packaging suitable for food slices, such as cheese slices, having a substantially rectangular flat shape, said packaging being comprised of a film being wound about the food slice to be packaged as a laid-flat tubing and completely enclosing said food slice, such that the two edge zones of the film extending along the longitudinal axis overlap and are mutually joined by means of a heat-sealing layer applied in the form of a strip close to and along, one edge zone of the film, said heat-sealing layer being essentially comprised of a heat-sealable olefin copolymer, characterized in that the outer surface of the packaging is provided with a coating comprising a silicon-based organic compound, in particular polydialkylsiloxane, and in that outside the area of the heat-sealing layer the film is provided with a print, if appropriate.
2. Packaging as claimed in claim 1, characterized in that said film is comprised of polyester, in particular polyethylene terephthalate, or of a polyolefin, in particular a propylene polymer.

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